This invention pertains to bicycle freewheel mechanisms for single speed bicycle motocross racing bicycles having a roller chain. In the past, such freewheel mechanisms have included an inner freewheel body which engages threads on a rear wheel hub, and an outer freewheel body, including an integral sprocket for engagement with the roller chain. A pair of pawls, and at least one pawl spring have been disposed between said inner and outer freewheel bodies, whereby forward rotation of the outer freewheel body would cause the pawls to engage and drive the inner freewheel body and rear wheel. Also, the pawls would allow the rear wheel to rotate in a forward direction when the outer freewheel body was rotating more slowly or was stopped.
In the past, two rows of steel balls have rotatably supported the outer freewheel body on the inner freewheel body, necessitating the use of hardened steel races, which has mandated steel construction, making previous freewheels unnecessarily heavy for racing purposes.
Also, previous freewheels have been difficult to remove and replace at the track where it is often necessary to rapidly change the rear sprocket for different conditions. A special freewheel removing tool and a long wrench have been needed, because, after some use, the inner freewheel body may become very difficult to loosen.
During a race, the cyclist is either pedalling, or he is braking, but he never coasts. Very small differences in friction are unimportant, because a bicycle motocross race lasts less than a minute
When the cyclist is pedalling, a freewheel has no friction, since the two races are locked up, and turn together. When braking, any freewheel friction only helps brake. Since the bicycle motocross racer never coasts, it follows that the extra friction created by the elimination of ball bearings in his freewheel is of no importance whatever. There is no penalty to be paid by the bicycle motocross racer, for not having ball bearings in his freewheel.
However, there are several advantages accruing with their elimination:
1. Without the steel balls, the freewheel doesn't have to have hardened steel races. Instead, it can be made mostly out of aluminum, which weighs about 1/3 as much.
2. If the balls are eliminated, the freewheel can become much simpler in construction, and it can become much easier to clean and oil, inspect, and to replace parts, if needed.
3. If the balls are eliminated, interchanging sprockets can become a much simpler thing to accomplish at the track, and it can be done in a different way, without removing the freewheel body from the hub at all. Special tools could be eliminated.
Thus, there are advantages to be gained in a racing freewheel which eliminates ball bearings. And so they are gained in the freewheel of this invention.